Thermal interface material and semiconductor device incorporating the same

ABSTRACT

A semiconductor device ( 10 ) includes a heat source ( 12 ), a heat-dissipating component ( 13 ) for dissipating heat generated by the heat source, and thermal interface material ( 14 ) filled in spaces formed between the heat source and the heat-dissipating component. The thermal interface material includes 100 parts by weight of alkenyl groups-containing organopolysiloxane, and Si—H groups-containing compound selected from the group consisting of organo-hydrogenpolysiloxane and polyorganohydrogensiloxane, and 800 to 1200 parts by weight of fillers consisting of aluminum powder having a mean particle size of 0.1 to 1 um and zinc oxide powder having a mean particle size of 1 to 5 um in a weight ratio of from 1/1 to 10/1 .

FIELD OF THE INVENTION

The present invention relates to a thermal interface material which isinterposable between a heat-generating electronic component and a heatdissipating component, and it also relates to a semiconductor deviceusing the thermal interface material.

DESCRIPTION OF RELATED ART

With the fast development of the electronics industry, advancedelectronic components such as CPUs (central processing units) are beingmade with ever faster operating speeds. During operation of the advancedelectronic components, much heat is generated. In order to ensure goodperformance and reliability of the electronic components, theiroperational temperature must be kept within a suitable range. Generally,a heat dissipating apparatus such as a heat sink or a heat spreader isattached to a surface of the electronic component, so that the heat istransferred from the electronic component to ambient air via the heatdissipating apparatus. However, the contact surfaces between the heatdissipating apparatus and the electronic component are rough andtherefore are separated from each other by a layer of interstitial airno mater how precisely the heat dissipating apparatus and the electroniccomponent are brought into contact. Thus, the contact resistance isrelatively high. A thermal interface material may be applied to thecontact surfaces to eliminate the air interstices between the heatdissipating apparatus and the electronic component in order to improveheat dissipation.

The thermal interface material includes base oil and fillers filled inthe base oil. The base oil is used for filling the air interstices tocreate an intimate contact between the heat dissipating apparatus andthe electronic component, whilst the fillers are used for improving thethermal conductivity of the thermal interface material to therebyincrease the heat dissipation efficiency of the heat dissipatingapparatus. However, the base oil may bleed from the thermal interfacematerial when exposed to heat for a long period of time. The thermalinterface material therefore tends to gradually harden, finally losingflexibility so that it peels off from the contact surfaces between theheat dissipating apparatus and the electronic component. This results inthe thermal interface material undesirably increasing its thermalresistance and the heat dissipating apparatus accordingly decreasing itsheat dissipation efficiency over time. The operational temperatures ofthe electronic components are undesirably increased, which leads todeterioration in their performance. Therefore, a thermal interfacematerial, which can prevent the base oil from bleeding, is needed.

SUMMARY OF THE INVENTION

The present invention relates, in one respect, to a thermal interfacematerial for electronic products, and in another respect, to asemiconductor device using the thermal interface material. According toa preferred embodiment of the present invention, the semiconductordevice includes a heat source, a heat-dissipating component fordissipating heat generated by the heat source, and a thermal interfacematerial filled in spaces formed between the heat source and theheat-dissipating component. The thermal interface material includes 100parts by weight of an alkenyl groups-containing organopolysiloxane, anda Si—H groups-containing compound selected from the group consisting oforgano-hydrogenpolysiloxane and polyorganohydrogensiloxane, and 800 to1200 parts by weight of fillers consisting of aluminum powder having amean particle size of 0.1 to 1 um and zinc oxide powder having a meanparticle size of 1 to 5 um in a weight ratio from 1/1 to 10/1.

Other advantages and novel features of the present invention will becomemore apparent from the following detailed description of preferredembodiment when taken in conjunction with the accompanying drawings, inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present thermal interface material can be betterunderstood with reference to the following drawings. The components inthe drawings are not necessarily drawn to scale, the emphasis insteadbeing placed upon clearly illustrating the principles of the presentthermal interface material. Moreover, in the drawings, like referencenumerals designate corresponding parts throughout the several views.

FIG. 1 is a schematic cross-sectional view of a semiconductor devicehaving a thermal interface material according to a preferred embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an electronic device 10 includes a heat source 12disposed on a circuit board 11, a heat-dissipating component 13 fordissipating heat generated by the heat source 12, and a thermalinterface material 14 filled in spaces formed between the heat source 12and the heat-dissipating component 13. The heat source 12 is anelectronic component, such as a central processing unit (CPU) of acomputer, which needs to be cooled. The heat-dissipating component 13 isa heat sink, which includes a base 131 and a plurality of fins 133disposed on the base 131. The heat-dissipating component 13 is attachedto the circuit board 11 via a resilient fixing member 15, which providesa resilient force for clamping the heat dissipation component 13 and thecircuit board 11 together. The base 131 of the heat-dissipatingcomponent 13 is sandwiched between the fixing member 15 and the circuitboard 11, and is urged downwardly towards the heat source 12 on thecircuit board 11 via the resilient force exerted thereon. The thermalinterface material 14 is pressed by the heat-dissipating component 13thus filled in the spaces formed between the heat source 12 and theheat-dissipating component 13.

The thermal interface material 14 is silicone grease composition havinghigh thermal conductivity, and includes a base oil and an amount offillers filled in the base oil.

The base oil makes up 100 parts by weight of the thermal interfacematerial 14. The base oil is cured silicone oil including threecomponents: component (A), component (B), and component (C).

Component (A) of the base oil is an organo-hydrogenpolysiloxane having achemical structure formula:

where a and b are positive numbers satisfying 0.01<a/(a+b)<0.4.Component (A) contains at least a Si—H group at side chains thereof.

Component (B) of the base oil is a polyorganohydrogensiloxane having oneof the following chemical structure formulas:

where, M_(e) is a methyl group, and component (B) contains at leastthree Si-bonded hydrogen atoms therein.

Component (C) of the base oil is an organopolysiloxane having a chemicalstructure formula:

where M_(e) is a methyl group, and m is larger than or equal to 2, sothat component (C) contains at least two alkenyl groups therein. Inaddition, m can also be numbered to satisfy a viscosity of component (C)being in a range from 50 to 5000 cps at 25° C.

The amount of components (A), (B), and (C) of the base oil is such thatthe ratio of the number of the alkenyl groups in component (C) to thenumber of the Si—H groups in component (A), and to the number of theSi-bonded hydrogens in component (B) is 4:1:3. Components (A), (B), and(C) of the base oil are used in such proportions that component (C),component (B), and component (A) are heat cured and cross linkedtogether to thereby obtain a composition with a satisfactorily networkedstructure, giving the thermal interface material a sufficient structureto prevent displacement of the base oil. Alternatively, the base oil mayinclude two components, i.e. component (A)/component (B), and component(C). With this composition, the ratio of Si—H groups in component(A)/component (B) to alkenyl groups in component (C) is 1:1, which heatcures and cross links the component (A)/component (B) and component (C)together to thereby obtain compositions with satisfactorily networkedstructures. The reaction formula for the Si—H groups and the alkenylgroups is:

The fillers are 800 to 1200 parts by weight of the thermal interfacematerial 14. The fillers are a mixture of aluminum powder and zinc oxidepowder in a weight ratio of from 1/1 to 10/1. The aluminum powder issubstantially spherical-shaped and has an average particle size from 1to 5 um. The zinc oxide powder is substantially spherical-shaped and hasan average particle size from 0.1 to 1 um.

The thermal interface material further includes a catalyst selected fromamong platinum and platinum compounds, which serves to promote additionreaction between alkenyl groups in component (C) and Si—H groups incomponent (A), and/or Si-bonded hydrogen in component (B). Exemplarycatalysts are elemental platinum, chloroplatinic acid, platinum-olefincomplexes, platinum-alcohol complexes, and platinum coordinatecompounds. An appropriate amount of the catalyst is 0.1 to 500 parts byweight of per million parts of component (C).

In the present electronic device 10, the thermal interface material 14is used to fill the spaces formed between the heat source 12 and theheat-dissipating component 13. After being dispersed, components (A),(B), and (C) cure with the heat produced by the heat source and thecatalyst blending thereinto. Once cured, the thermal interface material14 has a sufficient structure to prevent displacement of the base oiland a long-lasting flexibility to prevent its peeling off from the heatsource 12 or the heat-dissipating component 13. Therefore, the siliconecomposition ensures a high level of heat dissipation efficiency,improving the overall reliability of the electronic device 10.

In the present thermal interface material 14, examples of thesubstituted hydrocarbon group for methyl attached to a silicon atominclude alkyl groups such as ethyl, propyl, isopropyl, butyl, isobutyl,pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, decyl and dodecyl;aryl groups such as phenyl, tolyl, xylyl and naphthyl; aralkyl groupssuch as benzyl, phenylethyl and 2-phenylpropyl; alkenyl groups such asvinyl, allyl, propenyl, isopropenyl, 1-butenyl, 1-hexenyl, cyclohexenyland octenyl; and substituted ones of the foregoing groups in which someor all of the hydrogen atoms are substituted with halogen atoms (e.g.fluorine, bromine and chlorine), cyano groups or the like, such aschloromethyl, chloropropyl, bromoethyl, 3,3,3-trifluoropropyl andcyanoethyl.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present invention have been setforth in the foregoing description, together with details of thestructure and function of the invention, the disclosure is illustrativeonly, and changes may be made in detail, especially in matters of shape,size, and arrangement of portions within the principles of the inventionto the full extent indicated by the broad general meaning of the termsin which the appended claims are expressed.

1. A thermal interface material comprising: 100 parts by weight of baseoil; and 800 to 1200 parts by weight of fillers in the base oil; whereinthe base oil comprises Si—H groups contained in at least one oforgano-hydrogenpolysiloxane and polyorganohydrogensiloxane, and alkenylgroups contained in organopolysiloxane and cured with the Si—H groups.2. The thermal interface material as described in claim 1, wherein theorganopolysiloxane has a viscosity from 50 to 5000 cps at 25° C.
 3. Thethermal interface material as described in claim 1, wherein a ratio ofthe number of the alkenyl groups to the number of the Si—H groups is1:1.
 4. The thermal interface material as described in claim 1, whereina ratio of the number of the alkenyl groups in the organopolysiloxane tothe number of the Si—H groups in the organo-hydrogenpolysiloxane, and tothe number of the Si—H groups in polyorganohydrogensiloxane is 4:1:3. 5.The thermal interface material as described in claim 1, wherein theorgano-hydrogenpolysiloxane has a chemical structure formula as follows:

a and b herein are positive numbers satisfying 0.01<a/(a+b)<0.4.
 6. Thethermal interface material as described in claim 1, wherein a chemicalstructure formula of the polyorganohydrogensiloxane is one of:


7. The thermal interface material as described in claim 1, wherein thefillers are a mixture of aluminum powder and zinc oxide powder in aweight ratio from 1/1 to 10/1.
 8. The thermal interface material asdescribed in claim 7, wherein the aluminum powder has an averageparticle size of from 1 to 5 um, whilst the zinc oxide powder has anaverage particle size of from 0.1 to 1 um.
 9. The thermal interfacematerial as described in claim 1, further comprising a catalyst selectedfrom among platinum and platinum compounds, in such an amount as to give0.1 to 500 parts by weight of per million parts of theorganopolysiloxane.
 10. The thermal interface material as described inclaim 9, wherein the platinum compounds are chloroplatinic acid,platinum-olefin complexes, platinum-alcohol complexes, and platinumcoordinate compounds.
 11. A semiconductor device comprising: a heatsource; a heat-dissipating component for dissipating heat generated bythe heat source; and thermal interface material filled in spaces formedbetween the heat source and the heat-dissipating component, the thermalinterface material comprising: 100 parts by weight of alkenylgroups-containing organopolysiloxane, and Si—H groups-containingcompound selected from the group consisting oforgano-hydrogenpolysiloxane and polyorganohydrogensiloxane; 800 to 1200parts by weight of fillers consisting of aluminum powder having a meanparticle size of 0.1 to 1 um and zinc oxide powder having a meanparticle size of 1 to 5 um in a weight ratio from 1/1 to 10/1; and acatalyst selected from the group consisting of platinum and platinumcompounds, in such an amount as to give 0.1 to 500 parts by weight ofper million parts of the organopolysiloxane.
 12. The thermal interfacematerial as described in claim 11, wherein a ratio of the number of thealkenyl groups in the organopolysiloxane to the number of the Si—Hgroups in the organo-hydrogenpolysiloxane, and to the number of the Si—Hgroups in the polyorganohydrogensiloxane is 4:1:3.
 13. The thermalinterface material as described in claim 11, wherein theorgano-hydrogenpolysiloxane has a chemical structure formula:

a and b herein are positive numbers satisfying 0.01<a/(a+b)<0.4.
 14. Thethermal interface material as described in claim 11, wherein a chemicalstructure formula of the polyorganohydrogensiloxane is one of:


15. The thermal interface material as described in claim 11, wherein achemical structure formula of the organopolysiloxane is:

m herein being larger than or equal to 2.